ESD testing structure, method of using same and method of forming same

ABSTRACT

An electrostatic discharge (ESD) testing structure includes a measurement device in a first die. The ESD testing structure further includes a fuse in a second die. The ESD testing structure further includes a plurality of bonds electrically connecting the first die to the second die, wherein a first bond of the plurality of bonds electrically connects the fuse to the measurement device.

BACKGROUND

Electrostatic discharge (ESD) events occur when a large amount ofelectrical charge is discharged in a short amount of time. ESD eventspotentially damage active devices, passive devices and other structureswithin integrated circuits (ICs) due to high voltage or high current ofthe ESD event.

External testing devices are usable to measure ESD events. Externaltesting devices are connected to ICs at probe pads in order to measurethe current or voltage of the ESD event, in some instances. In someinstances, the external testing device remotely measures the ESD eventin order to avoid contact with the IC during the ESD event.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an electrostatic discharge (ESD) testingstructure in accordance with some embodiments.

FIG. 2 is a schematic view of an ESD testing structure in accordancewith some embodiments.

FIG. 3 is a schematic view of an ESD testing structure in accordancewith some embodiments.

FIG. 4 is a schematic view of a current recording structure for an ESDtesting structure in accordance with some embodiments.

FIGS. 5A-5C are schematic views of ESD testing structures in accordancewith some embodiments.

FIGS. 6A-6C are schematic view of ESD testing structures in accordancewith some embodiments.

FIG. 7 is a schematic view of an ESD testing/protection structure inaccordance with some embodiments.

FIG. 8 is a plan view of an ESD testing array in accordance with someembodiments.

FIGS. 9A and 9B are cross-sectional view of ESD testing structures inaccordance with some embodiments.

FIG. 10 is a flowchart of a method of using an ESD testing structure inaccordance with some embodiments.

FIG. 11 is a flowchart of a method of making an ESD testing structure inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, or the like, are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, or the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In some instances, semiconductor manufacturing processes cause chargesto build up on elements undergoing processing. Processes likegrinding/planarizing, sawing/dicing or cleaning cause charges to buildup on the elements during processing. A magnitude and location of thecharge build up depends on numerous factors including materials usedduring processing, processing rate and environmental conditions.

As device sizes decrease, integrated circuit (IC) formation usesthree-dimensional integrated circuits (3DIC) or 2.5-dimensionalintegrated circuits (2.5DIC) in order to form devices which have a samefunctional ability in less area on a substrate. 3DIC and 2.5DIC includebonding one die onto another element, such as a substrate, aninterposer, a fan out structure, another die, or another suitableelement. During a bonding process, such as a flip chip bonding process,elements are electrically bonded together to permit signals to travelbetween the die and the other element. In some instances, the built-upcharges are released during the bonding process resulting in anelectrostatic discharge (ESD) event. These ESD events are potentiallydamaging to elements being bonded together. For example, a surge ofcurrent or voltage damages transistors or other devices, in someinstances. External testing devices are limited in the ability toprecisely determine a location and/or magnitude of ESD events.

Precise determination of a location and magnitude of the ESD eventshelps to increase production yield by avoiding loss of product duringthe bonding process. In addition, the information about the location andmagnitude of the ESD events is usable to feed back into themanufacturing process in order to identify portions of the process whichimpart a significant amount of charge build up in order to attempt toreduce the amount of charge build up. In addition to modifyingprocesses, the ESD event information is usable to determine whether anyadditional protection structures are feasible. The ESD event informationis also usable to determine whether environmental controls aresufficient for a certain process.

An ESD testing structure formed as part of the elements undergoing thebonding process helps to precisely determine locations and magnitudes ofESD events. In some embodiments, an array of ESD testing structures isformed across a die in order to determine both magnitude and location ofESD events. By forming the testing structures directly on the die, theESD testing structures are able to measure current and/or voltage at thesite where the discharge occurs. This provides more precise datacollection than a remote measurement by an external device or ameasurement following completion of a bonding process. The ESD testingstructures are also capable of being formed as part of a protectionstructure to help reduce the risk of damage to a victim device during abonding process. A victim device is a device to be protected from theESD event.

The ESD testing structures are able to measure either voltage or currentand the type of measurement is selectable based on a desire of a user.In addition, the ESD testing structures are designed to be able todetermine the type of charge build up, i.e., positive charge or negativecharge, in some embodiments. This information is usable to help improvea semiconductor manufacturing process in order to improve yield.

FIG. 1 is a schematic view of an ESD testing structure 100 in accordancewith some embodiments. ESD testing structure 100 is located at aninterface 110 between a top die 112 and a bottom die 114. Bonds 115provide an electrical connection between top die 112 and bottom die 114.A measurement device 120, located in top die 112, is connected to one ofbonds 115 in order to measure the voltage or current of an ESD event. Afuse 130 is connected to measurement device 120 through bond 115. Fuse130 is capable of being selectively blown to prevent measurement device120 from being usable during a bonding process. ESD testing structure100 further includes probe pad A which is configured to be connected toground; probe pad B which is usable to obtain information related tomeasurement device 120 following a bonding process; and probe pad Cwhich is usable to test for an open circuit following the bondingprocess. Probe pad A is located on an opposite side of fuse 130 frommeasurement device 120. Probe pad B is located on an opposite side ofmeasurement device 120 from fuse 130. Probe pad C is connected to probepad A through a bond 115 which bypasses fuse 130. ESD testing structure100 also includes trimming pad TP1 and trimming pad TP2. Trimming padsTP1 and TP2 are usable to blow fuse 130 prior to the bonding process.Trimming pad TP1 is connected to a first side of fuse 130 between thefuse and a first bond 115. Trimming pad TP2 is connected to a secondside of fuse 130 between probe pad A and a second bond 115.

Interface 110 is a location where top die 112 and bottom die 114 meet.In some embodiments, a standoff distance exists between top die 112 andbottom die 114 such that the top die does not typically contact thebottom die. In some embodiments, at least one of top die 112 or bottomdie 114 is replaced by a substrate, an interposer, a fan out structureor another suitable element.

During manufacturing of top die 112 or bottom die 114, charges build upwithin the top die or bottom die or along a surface of the top die orbottom die. When the electrically conductive elements of bonds 115 comeinto contact, the built-up charges are able to move from one die to theother along the conductive path formed by bonds 115. This movement ofcharges is an ESD event.

Bonds 115 are electrical connections between top die 112 and bottom die114. In some embodiments, bonds 115 include copper pillars; solderbumps, conductive traces or other suitable electrical connectioncomponents. In some embodiments, bonds 115 are located completelybetween top die 112 and bottom die 114. In some embodiments, bonds 115prevent top die 112 from physically contacting bottom die 114 in orderto create the standoff height between the top die and the bottom die. Insome embodiments, bonds 115 are formed by a reflow process, a eutecticbonding process, or another suitable bonding process. In someembodiments where top die 112 physically contacts bottom die 114, afusion bonding process is used to form bonds 115 and to bond the top dieto the bottom die.

Measurement device 120 is configured to measure either a voltage duringan ESD event or a current during the ESD event. Measurement device 120is formed during the formation of other components of top die 112, suchas a functional device, dummy device or other components. By formingmeasurement device 120 during formation of other components of top die112, measurement device 120 has a same process corner as the othercomponents of the top die, i.e., manufacturing variation across a waferused to form top die 112 is the same for measurement device 120 and theother components. Having a same process corner will help with preciselymeasuring an impact of the ESD event on the components in top die 112.

In some embodiments, measurement device 120 includes a transistor, suchas a metal-oxide-semiconductor (MOS) transistor, configured as acapacitor. In some embodiments, measurement device 120 includes a diodeconnected transistor. In some embodiments, measurement device 120includes a plurality of diodes connected in series and/or in parallel.In some embodiments, measurement device 120 includes an array ofresistors and fuses.

Fuse 130 is usable to disable measurement device 120 prior to thebonding process. Fuse 130 is configured to form an open circuit, i.e.,be blown, if a current across the fuse exceeds a threshold value. Thethreshold value for fuse 130 is higher than a current which will destroymeasurement device 120 in order to ensure that fuse 130 remains intactduring the ESD event measured by the measurement device. In someembodiments, the threshold value ranges from about 10 milliamps (mA) toabout 20 mA. If the threshold value is too low, a risk ofunintentionally blowing fuse 130 increases, in some instances. If thethreshold value is too high, an amount of power for blowing fuse 130increases and a risk of damage to surrounding components in bottom die114 increases, in some embodiments.

Blowing fuse 130 is useful for omitting measurement device 120 fordetermining a location of the ESD event. In addition, blowing fuse 130permits selectively disabling measurement device 120 based on a type ofmeasurement performed by the measurement device. For example, if deviceswithin top die 112 or bottom die 114 are more susceptible to damage byhigh currents instead of by high voltages, fuses 130 associated withmeasurement devices 120 which measure voltage are blown, in someembodiments.

Fuse 130 includes a conductive component. In some embodiments, fuse 130includes a metallic material, silicide, a conductive polymer or anothersuitable conductive material. In some embodiments, fuse 130 is locatedin an interconnect structure of bottom die 114. In some embodiments,fuse 130 is in a first metal level of bottom die 114. In someembodiments, fuse 130 is a conductive line element. In some embodiments,fuse 130 is a conductive via element.

Probe pad A is usable for connecting ESD testing structure 100 to groundin order to determine whether measurement device 120 or fuse 130 wasdamaged during the ESD event. Probe pad A is located on a surface ofbottom die 114 separated from top die 112. In some embodiments, probepad A is located on a surface of bottom die 114 opposite from top die112. In some embodiments, probe pad A is located on a same surface ofbottom die 114 as top die 112 and is displaced from top die 112 in adirection parallel to interface 110. In some embodiments, a passivationlayer is formed over probe pad A following the bonding process in orderto reduce the risk of oxidation of probe pad A.

Probe pad B is usable for retrieving information measured by measurementdevice 120 following the ESD event.

Probe pad C is usable for determining whether there is an open circuitfollowing the bonding process. By probing probe pad C and probe pad A,the electrical connection through bond 115 is tested in order todetermine whether any open circuit measured by testing at probe pad B isthe result of damage to measurement device 120/fuse 130 or by a poorbonding process. Probe pads B and C are independently located on asurface of top die 112 separated from bottom die 114. In someembodiments, probe pads B and C are independently located on a surfaceof top die 112 opposite from bottom die 114. In some embodiments, probepads B and C are independently located on a same surface of top die 112as bottom die 114 and is displaced from bottom die 114 in a directionparallel to interface 110. In some embodiments, probe pad C is on a samesurface of top die 112 as probe pad B. In some embodiments, probe pad Cis on a different surface of top die 112 from probe pad B. In someembodiments, a passivation layer is formed over probe pad C followingthe bonding process in order to reduce the risk of oxidation of probepad C.

Trimming pad TP1 and trimming pad TP2 are usable to blow fuse 130 priorto the bonding process. Trimming pad TP1 or trimming pad TP2 are locatedbetween bottom die 114 and top die 112, in some embodiments. In someembodiments, trimming pad TP1 or trimming pad TP2 is separated from topdie 112. In some embodiments, at least one of trimming pad TP1 ortrimming pad TP2 is located on a same surface of bottom die 114 as probepad A. In some embodiments, at least one of trimming pad TP1 or trimmingpad TP2 is located on a surface of bottom die 114 different from probepad A. In some embodiments, at least one of trimming pad TP1 or trimmingpad TP2 is covered by a passivation layer before or after the bondingprocess to reduce the risk of oxidation.

Prior to the bonding process, a fuse 130 of selected ESD testingstructures is blown by applying a current from trimming pad TP1 totrimming pad TP2 of the selected ESD testing structures. In someembodiments, the ESD testing structures are selected based on a type ofelectrical property to be measured. For example, if only current of theESD event is to be measured, fuse 130 for voltage measuring ESD testingstructures is blown. In some embodiments, the ESD testing structures areselected based on a direction of the discharge of the ESD event. Forexample, if ESD testing structures which test a current flow from topdie 112 to bottom die 114 are used, fuses 130 of ESD testing structureswhich prohibit flow in this direction are blown. In some embodiments,the ESD testing structures are selected based on location. For example,fuses 130 of ESD testing structures outside of a selected area of bottomdie 114 are blown.

In use, ESD testing structure 100 measures the current or voltagedischarged between top die 112 and bottom die 114 during the bondingprocess using measurement device 120. For example, in some embodimentswhere measurement device 120 includes a capacitor, testing at probe padA and probe pad B will determine the amount of voltage stored in thecapacitor. In some embodiments where measurement device 120 includes anarray of resistors and fuses, probing at probe pad A and probe pad B todetermine a resistance between the two probe pads will determine anumber of the fuses the ESD event blew in order to determine a currentof the ESD event. Using diodes as the resistors is also able todetermine a direction of the current flow in order to help determine thetype of charge built up on each of top die 112 and bottom die 114. Othermeasurement device 120 structures will provide information on current orvoltage in different ways.

ESD testing structure 100 is closer to the actual location where thecharge release occurs and therefore is able to better determine theseverity of the ESD event in comparison with external measurementdevices. EST testing structure 100 also provides a significant amount offlexibility in determining whether to disable measurement device 120 incomparison with other structures which do not include fuse 130.

FIG. 2 is a schematic view of an ESD testing structure 200 in accordancewith some embodiments. ESD testing structure 200 is similar to ESDtesting structure 100. In comparison with ESD testing structure 100, ESDtesting structure 200 includes measurement device 120′ in place ofmeasurement device 120. ESD testing structure 200 is configured tomeasure a voltage of the ESD event. Measurement device 120′ is a MOStransistor configured as a capacitor.

During the ESD event, a voltage is stored in the capacitor ofmeasurement device 120′. By testing probe pads A, B and C, the voltagestored in the capacitor is retrieved for analysis. In some instances, avoltage of the ESD event exceeds a breakdown voltage of measurementdevice 120′. Testing at probe pads A, B and C will indicate thatmeasurement device 120′ no longer functions as a capacitor and permitscurrent to flow freely from probe pad B to probe pad A. While thisinformation indicates that the ESD event exceeded a certain value, theactual voltage value of the ESD event is not measured. In someembodiments, an array of capacitors connected in parallel, where eachcapacitor has a different breakdown voltage is included in measurementdevice 120′ in order to assist in determining the voltage level of theESD event when voltage level exceeds a breakdown voltage of one of thecapacitors. For example, in an ESD testing structure 200 including twocapacitors having different breakdown voltages, if one of the capacitorsis destroyed; and the other remains intact, the ESD event is determinedto have a voltage level between the two breakdown voltages of thecapacitors.

FIG. 3 is a schematic view of an ESD testing structure 300 in accordancewith some embodiments. ESD testing structure 300 is similar to ESDtesting structure 100. In comparison with ESD testing structure 100, ESDtesting structure 300 includes measurement device 120″ in place ofmeasurement device 120. ESD testing structure 300 is configured tomeasure a current of the ESD event. Measurement device 120″ is adiode-connected MOS transistor. Measurement device 120″ includes a PMOSdiode 120 a″ for permitting current flow from top die 112 to bottom die114; and a second diode 120 b″ for permitting current flow from bottomdie 114 to top die 112.

Measurement device 120″ is usable in combination with a currentrecording structure to determine a magnitude of a current during the ESDevent. In some embodiments, the current recording structure is betweenmeasurement device 120″ and probe pad B. In some embodiments, thecurrent recording structure is between measurement device 120″ and bond115. In some embodiments, the current recording structure includes anarray of resistors and fuses.

FIG. 4 is a schematic view of a current recording structure 400 for anESD testing structure in accordance with some embodiments. Currentrecording structure 400 is usable with an ESD testing structure forstoring information related to a current of an ESD event. Currentrecording structure 400 is usable in combination with a measurementdevice, such as measurement device 120 (FIG. 1) or measurement device120″ (FIG. 3). In some embodiments, current recording structure 400replaces the measurement device, e.g., measurement device 120,measurement device 120′ or measurement device 120″.

Current recording structure 400 includes an array of resistors R_DUT1,R_DUT2, R_DUT3 . . . R_DUTx (collectively referred to as resistorsR_DUT). Resistors R_DUT are connected in parallel. Current recordingstructure 400 also includes an array of fuses R_fuse1, R_fuse2, R_fuse3. . . R_fusex (collectively referred to as fuses R_fuse). Each resistorof resistors R_DUT is connected in series with a corresponding fuse offuses R_fuse. Each combination of resistor R_DUT and fuse R_fuse createsa specific current, e.g., current I1, I2, I3 . . . Ix, based on theresistance value of the respective resistor and fuse and a voltage ofthe ESD event. Selecting a resistance of resistors R_DUT and thresholdvalues for fuses R_fuse, a precise measurement of a current of the ESDevent is recorded in current recording structure 400.

Fuses R_fuse have a resistance value and generate heat based on theresistance value. Once the heat exceeds the threshold value, the fusebreaks, i.e., is blown, and the electrical connection provided by thefuse is open. The threshold value of fuses R_fuse is independentlyselected during a manufacturing process. In some embodiments, thethreshold value is selected based on a material of fuses R_fuse;geometrical dimensions of fuses R_fuse; connections to fuses R_fuse; orother suitable selections. Fuses R_fuse independently have a thresholdvalue ranging from about 8 mA to about 20 mA. If the threshold value istoo low, a risk of blowing a fuse prior to the ESD event increases, insome instances. If the threshold value is too high, a risk of notrecording any current for the ESD event increases, in some instances.The maximum threshold value for fuses R_fuse is less than the thresholdvalue for fuse 130 of an ESD testing structure, e.g., ESD testingstructure 100 or ESD testing structure 120″. If the maximum thresholdvalue for fuses R_fuse exceeds the threshold value for fuse 130, a riskof blowing fuse 130 instead of fuses in current recording structure 400increases, in some instances. In some embodiments, each of fuses R_fusehas a same threshold value. In some embodiments, at least one fuse offuses R_fuse has a different threshold value from another fuse of fusesR_fuse.

Fuses R_fuse are formed in an interconnect structure of an ESD testingstructure. In some embodiments, each of fuses R_fuse is formed on a samelevel of an interconnect structure. In some embodiments, at least onefuse of fuses R_fuse is formed on a different level of an interconnectstructure from another fuse of fuses R_fuse. In some embodiments, eachof fuses R_fuse is formed on a same level of an interconnect structureas fuse 130. In some embodiments, at least one fuse of fuses R_fuse isformed on a different level of an interconnect structure from fuse 130.

Resistors R_DUT are formed in an interconnect structure of the ESDtesting structure or in a front-end, i.e., within a substrate, of theESD testing structure. In some embodiments, each resistor of resistorsR_DUT is formed in the front-end of the ESD testing structure. In someembodiments, each resistor of resistors R_DUT is formed in theinterconnect structure of the ESD testing structure. In someembodiments, at least one resistor of resistors R_DUT is formed in thefront-end and another resistor of resistors R_DUT is formed in theinterconnect structure. In some embodiments, each of resistors R_DUT isformed on a same level of the interconnect structure. In someembodiments, at least one resistor of resistors R_DUT is formed on adifferent level of the interconnect structure from another resistor ofresistors R_DUT. In some embodiments, each of resistors R_DUT is formedon a same level of an interconnect structure as fuse 130. In someembodiments, at least one resistor of resistors R_DUT is formed on adifferent level of an interconnect structure from fuse 130.

A resistance of each of resistors R_DUT is selected during themanufacturing process. The resistance of each of resistors R_DUT isindependently selected based on a material and/or geometric dimension ofresistors R_DUT. In some embodiments, each of resistors R_DUT has a sameresistance. In some embodiments, at least one resistor of resistorsR_DUT has a different resistance from another resistor of resistorsR_DUT.

A combination of a resistor, e.g., R_DUT1, and a fuse, e.g., R_fuse1,determines a current, e.g., I1, passing along a leg of current recordingstructure 400. Each leg of current recording structure 400 is configuredto have a different current value. In some embodiments, the currentvalue along each leg is selected by changing the resistance of resistorsR_DUT, as discussed above. For example, in some embodiments, aresistance imparted by each of fuses R_fuse is constant across currentrecording structure 400 and the resistance of each of resistors R_DUT isdifferent from each other resistor. In some embodiments, the currentvalue along each leg is selected by changing the resistance imparted byfuses R_fuse. For example, in some embodiments, a resistance imparted byeach of fuses R_fuse is different from every other fuse and theresistance of each of resistors R_DUT is constant across currentrecording structure 400. In some embodiments, the resistance is selectedby changing the resistance of resistor R_DUT and the resistance impartedby fuses R_fuse. For example, in some embodiments, the resistance ofresistor R_DUT1 is equal to the resistance of resistor R_DUT2, but theresistance imparted by fuse R_fuse1 is different from the resistanceimparted by fuse R_fuse2; and the resistance of resistor R_DUT3 isdifferent from the resistance of resistor R_DUT1 or R_DUT2, but theresistance imparted by fuse R_fuse3 is a same resistance as fuse R_fuse1or R_fuse2.

In operation, current recording structure 400 carries a current acrosseach leg based on the combined resistance of resistors R_DUT and fusesR_fuse. The current value is determined based on the materials andgeometric dimensions of resistors R_DUT and fuses R_fuse. As the currentmagnitude of the ESD event increases, a number of blown fuses of currentrecording structures 400 increases. Probing an ESD testing structure,e.g., ESD testing structure 100 or ESD testing structure 300, permits adetermination of which fuses of current recording structure 400 areblown based on a measured voltage drop from probe pad B to probe pad Aand the known resistances of legs of the current recording structure400.

Identifying which fuses R_fuse are blown determines a range of thecurrent magnitude of the ESD event. The range is from the highestthreshold value of the blown fuses to the lowest threshold value of thenon-blown fuses. The scale of the range depends on a number of fuses incurrent recording structure 400. As the number of fuses increases, thegradations of the range between threshold values of fuses decreases; buta size of current recording structure 400 increases. If the ESD eventfails to blow any of fuses R_fuse, then the current of the ESD event isdetermined to be less than a smallest recordable current of currentrecording structure 400.

Using ESD testing structure 300 as an example, in some embodiments,current recording structure 400 is connected between measurement device120″ and probe pad B. In some embodiments, current recording structure400 is connected between measurement device 120″ and bond 115. In someembodiments, current recording structure is connected between bond 115and fuse 130. In some embodiments, current recording structure 400replaces the measurement device, e.g., measurement device 120,measurement device 120′ or measurement device 120″.

FIG. 5A is a schematic view of an ESD testing structure 500 inaccordance with some embodiments. ESD testing structure 500 is similarto ESD testing structure 300. In comparison with ESD testing structure300, ESD testing structure 500 includes measurement device 520 in placeof measurement device 120″. Measurement device 520 includes twoseries-connected NMOS diodes. In some embodiments, measurement device520 includes greater or fewer number of series-connected NMOS diodes.NMOS diodes restrict a direction of current flow in ESD testingstructure 500. If the ESD event discharges current in a direction notpermitted by ESD testing structure 500, a current recording structurewithin measurement device 520, e.g., current recording structure 400included as part of measurement device 520, in ESD testing structure 500will not include any blown fuses. By determining a direction ofdischarge in the ESD event, ESD structure provides information regardingwhat type of charge is built up on top die 112 and bottom die 114.

FIG. 5B is a schematic view of an ESD testing structure 500′ inaccordance with some embodiments. In comparison with ESD testingstructure 500, ESD testing structure 500′ includes measurement device520′ in place of measurement device 520, which includes twoseries-connected PMOS diodes. In some embodiments, measurement device520′ includes greater or fewer number of series-connected PMOS diodes.PMOS diodes restrict a direction of current flow in ESD testingstructure 500′ to be opposite of a current flow direction permitted byESD testing structure 500. In some embodiments, ESD testing structuresinclude a combination of ESD testing structure 500 and ESD testingstructure 500′ in order to obtain information related to both adirection and magnitude of a discharge during the ESD event.

FIG. 5C is a schematic view of an ESD testing structure 500″ inaccordance with some embodiments. In comparison with ESD testingstructure 500, ESD testing structure 500″ includes measurement device520″ in place of measurement device 520, which includes twoseries-connected NMOS diodes connected in parallel with two otherseries-connected PMOS diodes. In some embodiments, separate currentrecording structures, e.g., multiple current recording structures 400included as part of measurement device 520″, are connected betweendiodes of the PMOS diodes and between diodes of the NMOS diodes. In someembodiments, measurement device 520″ includes greater or fewer number ofseries-connected PMOS diodes or series-connected NMOS diodes and greateror fewer number of diode arrangements connected in parallel. This typeof arrangement reduces an area of a device which includes two separateESD testing structures, e.g., ESD testing structure 500 and ESD testingstructure 500′. In some embodiments, a single current recordingstructure is connected to both the PMOS diodes and the NMOS diodes whena direction of the discharge of the ESD event is not measured by ESDtesting structure 500″.

FIG. 6A is a schematic view of an ESD testing structure 600 inaccordance with some embodiments. ESD testing structure 600 is similarto ESD testing structure 300. In comparison with ESD testing structure300, ESD testing structure 600 includes measurement device 620 in placeof measurement device 120″. Measurement device 620 includes twoseries-connected of diodes for restricting a direction of current flowin ESD testing structure 600. In some embodiments, measurement device620 includes greater or fewer number of series-connected diodes. Incomparison with measurement device 520, measurement device 620 is notlimited to a MOS transistor structure.

FIG. 6B is a schematic view of an ESD testing structure 600′ inaccordance with some embodiments. In comparison with ESD testingstructure 600, ESD testing structure 600′ includes measurement device620′ in place of measurement device 620, which includes twoseries-connected diodes for restriction a direction of current flow inESD testing structure 600′ to be opposite of a current flow directionpermitted by ESD testing structure 600. In some embodiments, measurementdevice 620′ includes greater or fewer number of series-connected diodes.In some embodiments, ESD testing structures include a combination of ESDtesting structure 600 and ESD testing structure 600′ in order to obtaininformation related to both a direction and magnitude of a dischargeduring the ESD event.

FIG. 6C is a schematic view of an ESD testing structure 600″ inaccordance with some embodiments. In comparison with ESD testingstructure 600, ESD testing structure 600″ includes measurement device620″ in place of measurement device 620, which includes twoseries-connected diodes connected in parallel with another twoseries-connected diodes. The first two series-connected diodes permitscurrent flow in a first direction and the second two series-connecteddiodes permits current flow in a second direction opposite the firstdirection. In some embodiments, measurement device 620″ includes greateror fewer number of the first series-connected diodes or the secondseries-connected diodes and greater or fewer number of diodearrangements connected in parallel. In some embodiments, separatecurrent recording structures, e.g., multiple current recordingstructures 400 included as part of measurement device 620″, areconnected between diodes of the first series diodes and between diodesof the second series diodes. This type of arrangement reduces an area ofa device which includes two separate ESD testing structures, e.g., ESDtesting structure 600 and ESD testing structure 600′. In someembodiments, a single current recording structure is connected to boththe first series diodes and the second series diodes when a direction ofthe discharge of the ESD event is not measured by ESD testing structure600″.

FIG. 7 is a schematic view of an ESD testing/protection structure 700 inaccordance with some embodiments. ESD testing/protection structure 700is similar to ESD testing structure 100. In comparison with ESD testingstructure 100, ESD testing structure 700 includes a victim device 740connected in parallel with measurement device 120. A fuse 750 isconnected between measurement device 120 and victim device 740. Insteadof only measuring the discharge of the ESD event, ESD testing/protectionstructure 700 also provides protection for victim device 740.

For example, in some embodiments where measurement device 120 isconfigured to measure a voltage, a breakdown voltage of measurementdevice 120 is lower than a damaging voltage level for victim device 740.This means that measurement device 120 will create a low resistance pathfor the ESD event and reduce the risk of damage to victim device 740.

Fuse 750 permits disabling of measurement device 120 following thebonding process. By disabling measurement device 120 following thebonding process, parasitic properties associated with measurement device120 which could potentially impact the functionality of victim device740 are removed. Fuse 750 is blown by applying a sufficient voltage toprobe pad B and connecting probe pad A to ground.

FIG. 8 is a plan view of an ESD testing array 800 in accordance withsome embodiments. ESD testing array 800 is part of a die, e.g., top die112. ESD testing array 800 includes a plurality of current measuring ESDtesting structures 810, e.g., ESD testing structure 300, and a pluralityof voltage measuring ESD testing structures 820, e.g., ESD testingstructure 200. Including current measuring ESD testing structures 810and voltage measuring ESD testing structures 820 helps to identifywhether an ESD event is a localized discharge or whether the dischargeis uniform across the die.

In some embodiments, locations for current measuring ESD testingstructures 810 are determined based on empirical data. In someembodiments, locations for current measuring ESD testing structures 810are based on a location of highly sensitive components of the die. Insome embodiments, locations for current measuring ESD testing structures810 are random. In some embodiments, locations for current measuring ESDtesting structures 810 are based on a predetermined pattern. Similarly,locations for voltage measuring ESD testing structures 820 are based onempirical data, location of highly sensitive components, randomplacement or predetermined patterns, in some embodiments.

ESD testing array 800 does not include current measuring ESD testingstructures 810 adjacent to each other along a row or column of thearray. In some embodiments, current measuring ESD testing structures 810are located adjacent to each other along a row or column of the array.In some embodiments, a number of current measuring ESD testingstructures 810 and voltage measuring ESD testing structures 820 in ESDtesting array 800 is based on an amount of available space on the die.For example, after locations of functional components of the die areselected, current measuring ESD testing structures 810 and voltagemeasuring ESD testing structures 820 are added into available locationsin order. In some instances, adding current measuring ESD testingstructures 810 and voltage measuring ESD testing structures 820 intoavailable space helps to increase uniformity of a manufacturing processby smoothing out differences in pattern densities.

FIG. 9A is a cross-sectional view of an ESD testing structure 900 inaccordance with some embodiments. ESD testing structure 900 is similarto ESD testing structure 100. In comparison with ESD testing structure100, ESD testing structure 900 includes a third die 960 above top die112, such that top die 112 is between bottom die 114 and third die 960.ESD testing structure 900 is an exemplary structure resulting frombonding third die 960 to top die 112 in a 3DIC structure. In someembodiments, third die 960 physically contacts top die 112 to form aninterface 910. In some embodiments, a standoff height exists betweenthird die 960 and top die 112.

ESD testing structure 900 includes all the components of ESD testingstructure 100. ESD testing structure 900 further includes a measurementdevice 920 in third die 960. Bonds 915 electrically connect third die960 to top die 112. A fuse 930 is in top die 112. Probe pads A′, B′ andC′ are similar to probe pads A, B, and C. Possible locations of probepads A′, B′ and C′ are similar to those discussed above with respect toprobe pads A, B, and C; adjusted to refer to top die 112 and third die960 instead of bottom die 114 and top die 112. Trimming pads TP1′ andTP2′ are similar to trimming pads TP1 and TP2. Possible locations oftrimming pads TP1′ and TP2′ are similar to those discussed above withrespect to trimming pads TP1 and TP2; adjusted to refer to top die 112and third die 960 instead of bottom die 114 and top die 112. Componentsof ESD testing structure 900 are formed in a similar manner as thatdescribed above with respect to ESD testing structure 100.

ESD testing structure 900 is usable to measure an ESD event which occursas a result of bonding third die 960 to top die 112. ESD testingstructure 900 is capable is disabling measurement device 920 followingbonding of top die 112 to bottom die 114, but prior to bonding third die960 to top die 112.

In some embodiments, measurement device 120 has a same structure asmeasurement device 920. In some embodiments, measurement device 920 hasa different structure from measurement device 120. In some embodiments,measurement device 120 is configured to measure a different electricalparameter, e.g., voltage or current, from measurement device 920. Insome embodiments, measurement device 120 is configured to measure a sameelectrical parameter as measurement device 920.

FIG. 9B is a cross-sectional view of an ESD testing structure 900′ inaccordance with some embodiments. ESD testing structure 900′ is similarto ESD testing structure 900. In comparison with ESD testing structure900, ESD testing structure 900′ includes a fuse 930′ and trimming padsTP1″ and TP2″ in bottom die 114 instead of top die 112. Electricalconnections extend from bonds 915 through top die 112 to bonds 915′ inorder to electrically connect measurement device 920 to fuse 930′.

ESD testing structure 900′ is capable of functioning in a similar manneras ESD testing structure 900 despite the location of fuse 930′ in bottomdie 114. The arrangement of ESD testing structure 900′ is usable when anamount of free space in bottom die 114 is greater than an amount of freespace in top die 112. For example, when bottom die 114 is fan outstructure or an interposer, the amount of area of bottom die 114occupied by functional elements is less than that in top die 112, insome embodiments.

FIG. 10 is a flowchart of a method 1000 of using an ESD testingstructure in accordance with some embodiments. In operation 1002,testing structures to be trimmed are identified. In some embodiments,the testing structures are identified based on a location of the testingstructure on the die. In some embodiments, the testing structures areidentified based on proximity to a functional component. In someembodiments, the testing structures are identified based on a type ofelectrical parameter measured. In some embodiments, the testingstructures are identified automatically based on information availableto a processor configured to identify testing structure based on any ofthe above criteria. In some embodiments, the testing structures areidentified by a user.

In operation 1004, the identified testing structures are trimmed.Trimming the testing structures includes disabling a measurement deviceof the testing structure. In some embodiments, trimming the identifiedtesting structure includes blowing a fuse. In some embodiments, the fuseis blow by applying a sufficient voltage to trimming pads of the testingstructure.

In operation 1006, a die is bonded to a device structure. The dieincludes functional components as well as a measurement device formeasuring an ESD event during the bonding process. The measurementdevice is electrically connected to a fuse of the testing structure bythe bonding process. In some embodiments, the bonding process includes areflow process, a eutectic bonding process, a fusion bonding process ora hybrid bonding process. The measurement device is disabled by thetrimming process in operation 1004 for all identified testingstructures.

Measurement device which remain enabled following operation 1004 collectinformation related to any ESD event which occurs during the bondingprocess. In some embodiments, the measurement device captures a currentor a voltage of the ESD event. In some embodiments, the die includes aplurality of measurement devices and the plurality of measurementdevices provide information related to a location of the ESD event.

In some embodiments, the device structure includes another die, asubstrate, an interposer, a fan-out structure or another suitabledevice. In some embodiments, the bonding process results in the diephysically contacting the device structure. In some embodiments, thebonding process results in a standoff height between the die and thedevice structure.

In operation 1008, the non-trimmed testing structures are probed inorder to retrieve information related to an ESD event during the bondingprocess. In some embodiments, probing the non-trimmed testing structuresincludes determining whether an open circuit remains following thebonding process. In some embodiments, probing the non-trimmed testingstructure includes retrieving information related to a voltage of theESD event. In some embodiments, probing the non-trimmed testingstructure includes retrieving information related to a current of theESD event. Other aspect and locations for the probing process aredescribed above.

In operation 1010, a voltage and/or a current of the ESD event isdetermined. In some embodiments, the voltage is determined based onbreaking down of a device having a known breakdown voltage. In someembodiments, the voltage is determined based on a voltage stored in acapacitor. In some embodiments, the current is determined based on ameasurement of a resistance through an array of resistors and fuses. Insome embodiments, determining the current of the ESD event includesdetermining a direction of the current. In some embodiments, determiningthe voltage and/or the current includes determine a possible range forthe voltage and/or the current of the ESD event.

In optional operation 1012, a location of the ESD event is determined.The location of the ESD event is determined by comparing informationretrieved from testing structures across the die. In some embodiments,operation 1012 is omitted. Operation 1012 is omitted if a location ofthe ESD event is unnecessary, in some instances.

In optional operation 1014, the voltage and/or the current of the ESDeven is used to modify a manufacturing process or environmentalcontrols. In some embodiments, the location information from operation1012 is used to modify the manufacturing process or environmentalcontrols.

The modification of the manufacturing process is used to reduce theaccumulation or the location of charged particles on the die or thedevice structure in order to reduce a magnitude or location of an ESDevent. In some embodiments, the manufacturing process is modified byadding a rinsing step to removed charged particles from the die or thedevice structure. In some embodiments, the manufacturing process ismodified to change a grinding process or a dicing process. In someembodiments, the manufacturing process is modified by changing amaterial used during a cleaning process. In some embodiments, themanufacturing process is modified to alter a location of the ESD eventby using magnetic forces to re-distribute charged particles within thedie or the device structure.

The environmental controls are modified to help remove charged particlesfrom an ambient environment of the manufacturing process. In someembodiments, modifying the environmental controls includes adjustingfilters for the ambient air; providing additional static removalprocesses for operators entering the manufacturing area or othersuitable environmental modifications.

In some embodiments, operation 1014 is omitted if the magnitude andlocation of the ESD event do not pose a risk of damaging the die or thedevice structure.

In some embodiments, an order of operations for method 1000 is changed.For example, in some embodiments, operation 1012 is performed prior tooperation 1010. In some embodiments, additional operations are added.For example, in some embodiments, a passivation layer is formed overprobe pads following operation 1008. In some embodiments, at least oneoperation is omitted. For example, in some embodiments, operation 1012is omitted.

Method 1000 is usable with ESD testing structures described above orother suitable ESD testing structures. In some embodiments, severaldifferent structures or types of ESD testing structures are combined inorder to implement method 1000.

FIG. 11 is a flowchart of a method 1100 of forming an ESD testingstructure in accordance with some embodiments. In operation 1102, atrimming section is formed in a first die. The trimming section includesa fuse electrically connected between two trimming pads, e.g., fuse 130between trimming pads TP1 and TP2. In some embodiments, the fuse isformed in an interconnect structure of the first die. In someembodiments, forming the trimming section includes a photolithographyprocess to form openings in the interconnect structure followed adeposition process to fill the openings with conductive material. Insome embodiments, a planarization process or an etching process is usedto remove excess conductive material following the deposition process.In some embodiments, the first die includes functional components. Insome embodiments, the first die includes a substrate, an interposer, afan-out structure or another suitable structure.

In operation 1104, a measurement device is formed in a second die. Thesecond die includes functional components. In some embodiments, formingthe measurement device includes forming a capacitor. In someembodiments, forming the measurement device includes forming at leastone diode. In some embodiments, forming the measurement device alsoincludes forming a current recording structure which includes an arrayof resistors and fuses. In some embodiments, forming the measurementdevice includes a series of implantation; deposition; photolithography;annealing or planarization processes. In some embodiments, forming themeasurement device includes forming the measurement device in afront-end of the second die. In some embodiments, forming themeasurement device includes forming at least a portion of themeasurement device in an interconnect structure of the second die.

In operation 1106, the first die is bonded to the second die. Bondingthe first die to the second die electrically connects the trimmingsection to the measurement device. In some embodiments, the bondingincludes a reflow process, a eutectic bonding process, a fusion bondingprocess or a hybrid bonding process.

In optional operation 1108, an additional trimming section is formed inthe first die. The additional trimming section is spaced away from thetrimming section formed in operation 1102. The additional trimmingsection is formed in a location which is not covered by the second diein the bonding operation of 1106. In some embodiments, the additionaltrimming section is formed simultaneously with operation 1102. In someembodiments, the additional trimming section is formed before or afteroperation 1102. In some embodiments where no third die is bonded to thesecond die, operation 1108 is omitted. In some embodiments where method1100 includes operation 1110, operation 1108 is omitted.

In optional operation 1110, a trimming section is formed in the seconddie. The trimming section is similar to the trimming section formed inoperation 1102. In some embodiments, the trimming section is formed inan interconnect structure of the second die. In some embodiments,forming the trimming section includes a photolithography process to formopenings in the interconnect structure followed a deposition process tofill the openings with conductive material. In some embodiments, aplanarization process or an etching process is used to remove excessconductive material following the deposition process. In someembodiments where no third die is bonded to the second die, operation1110 is omitted. In some embodiments where method 1100 includesoperation 1108, operation 1110 is omitted.

In optional operation 1112, a measurement device is formed in a thirddie. The third die includes functional components. In some embodiments,forming the measurement device includes forming a capacitor. In someembodiments, forming the measurement device includes forming at leastone diode. In some embodiments, forming the measurement device alsoincludes forming a current recording structure which includes an arrayof resistors and fuses. In some embodiments, forming the measurementdevice includes a series of implantation; deposition; photolithography;annealing or planarization processes. In some embodiments, forming themeasurement device includes forming the measurement device in afront-end of the third die. In some embodiments, forming the measurementdevice includes forming at least a portion of the measurement device inan interconnect structure of the third die. In some embodiments, themeasurement device in the third die has a same structure as themeasurement device in the second die. In some embodiments, themeasurement device in the second die has a different structure from themeasurement device in the third die. In some embodiments where no thirddie is bonded to the second die, operation 1112 is omitted.

In optional operation 1114, the third die is bonded to the second die.In some embodiments, bonding the third die to the second dieelectrically connects the trimming section in the first die to themeasurement device in the third die. In some embodiments, bonding thethird die to the second die electrically connects the trimming sectionin the second die to the measurement device in the third die. In someembodiments, the bonding includes a reflow process, a eutectic bondingprocess, a fusion bonding process or a hybrid bonding process. In someembodiments a bonding process in operation 1114 is a same bondingprocess as in operation 1106. In some embodiments, the bonding processin operation 1114 is a different bonding process from operation 1106. Insome embodiments where no third die is bonded to the second die,operation 1114 is omitted.

In some embodiments, an order of operations for method 1100 is changed.For example, in some embodiments, operation 1104 is performed prior tooperation 1102. In some embodiments, additional operations are added.For example, in some embodiments, a passivation layer is formed overprobe pads prior to operation 1114. In some embodiments, at least oneoperation is omitted. For example, in some embodiments, operation 1108is omitted.

Method 1100 is usable to form ESD testing structures described above orother suitable ESD testing structures. In some embodiments, method 1100is repeated to form several different structures or types of ESD testingstructures in a same die in order to determine a location of an ESDevent during a bonding process.

One aspect of this description relates to an electrostatic discharge(ESD) testing structure. The ESD testing structure includes ameasurement device in a first die. The ESD testing structure furtherincludes a fuse in a second die. The ESD testing structure furtherincludes a plurality of bonds electrically connecting the first die tothe second die, wherein a first bond of the plurality of bondselectrically connects the fuse to the measurement device.

Another aspect of this description relates to an electrostatic discharge(ESD) testing structure. The ESD testing structure includes a firstmeasurement device in a first die. The ESD testing structure furtherincludes a first fuse in a device structure. The ESD testing structurefurther includes a second measurement device in a second die. The ESDtesting structure further includes a second fuse outside the second die.The ESD testing structure further includes a first plurality of bondselectrically connecting the first die to the device structure, wherein abond of the first plurality of bonds electrically connects the firstmeasurement device to the first fuse. The ESD testing structure furtherincludes a second plurality of bonds electrically connecting the seconddie to the first die, wherein a bond of the second plurality of bondselectrically connects the second measurement device to the second fuse.

Still another aspect of this description relates to a method of using anelectrostatic discharge (ESD) testing structure. The method includesbonding a die to a device structure, wherein bonding the die to thedevice structure comprises electrically connecting each measurementdevice of a plurality of measurement devices in the die to acorresponding fuse of a plurality of fuses in the device structure toform a plurality of ESD testing structures. The method further includestrimming at least one fuse of the plurality of fuses, wherein trimmingthe at least one fuse disables a corresponding measurement device of theplurality of measurement devices. The method further includes capturinga voltage or a current of an ESD event during bonding the die to thedevice structure using non-disabled measurement devices of the pluralityof measurement devices. The method further includes probing at least onenon-disabled measurement device of the plurality of measurement devicesof the second set of ESD testing structures.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An electrostatic discharge (ESD) testingstructure comprising: a measurement device in a first die; a fuse, afirst trim pad, and a second trim pad in a second die; and a pluralityof bonds electrically connecting the first die to the second die,wherein a first bond of the plurality of bonds electrically connects thefuse to the measurement device, the first trim pad is electricallyconnected to a first side of the fuse, and the second trim pad iselectrically connected to the second side of the fuse.
 2. The ESDtesting structure of claim 1, wherein the measurement device isconfigured to detect a voltage during an ESD event.
 3. The ESD testingstructure of claim 2, wherein the measurement device comprises acapacitor.
 4. The ESD testing structure of claim 1, wherein themeasurement device is configured to detect a current during an ESDevent.
 5. The ESD testing structure of claim 4, wherein the measurementdevice comprises at least one diode.
 6. The ESD testing structure ofclaim 5, wherein the measurement device further includes a currentrecording structure.
 7. The ESD testing structure of claim 6, whereinthe current recording structure is electrically between the at least onediode and the fuse.
 8. The ESD testing structure of claim 6, wherein theat least one diode is between the fuse and the current recordingstructure.
 9. The ESD testing structure of claim 6, wherein the currentrecording structure comprises: a plurality of resistors; and a pluralityof fuses, wherein each resistor of the plurality of resistors iselectrically connected in series with a corresponding fuse of theplurality of fuses.
 10. The ESD testing structure of claim 9, whereineach fuse of the plurality of fuses has a different threshold value forblowing the corresponding fuse.
 11. The ESD testing structure of claim1, further comprising a second fuse between the measurement device andthe first bond, wherein the measurement device is configured toelectrically connect in parallel with a victim device.
 12. The ESDtesting structure of claim 1, further comprising: a plurality ofmeasurement devices in the first die; and a plurality of fuses in thesecond die, wherein each measurement device of the plurality ofmeasurement devices is electrically connected to a corresponding fuse ofthe plurality of fuses through a corresponding bond of the plurality ofbonds.
 13. An electrostatic discharge (ESD) testing structurecomprising: a first measurement device in a first die; a first fuse in adevice structure; a second measurement device in a second die; a secondfuse outside the second die; a first plurality of bonds electricallyconnecting the first die to the device structure, wherein a bond of thefirst plurality of bonds electrically connects the first measurementdevice to the first fuse; and a second plurality of bonds electricallyconnecting the second die to the first die, wherein a bond of the secondplurality of bonds electrically connects the second measurement deviceto the second fuse.
 14. The ESD testing structure of claim 13, whereinthe second fuse is in the first die.
 15. The ESD testing structure ofclaim 13, wherein the second fuse is in the device structure.
 16. TheESD testing structure of claim 15, further comprising a conductivestructure extending through the first die to electrically connect thesecond measurement device to the second fuse.
 17. The ESD testingstructure of claim 13, wherein a structure of the first measurementdevice is a same structure as the second measurement device.
 18. The ESDtesting structure of claim 13, wherein a structure of the firstmeasurement device is different from a structure of the secondmeasurement device.
 19. A method of using an electrostatic discharge(ESD) testing structure, the method comprising: bonding a die to adevice structure, wherein bonding the die to the device structurecomprises electrically connecting each measurement device of a pluralityof measurement devices in the die to a corresponding fuse of a pluralityof fuses in the device structure to form a plurality of ESD testingstructures; trimming at least one fuse of the plurality of fuses priorto the bonding of the die to the device structure, wherein trimming theat least one fuse disables a corresponding measurement device of theplurality of measurement devices; capturing a voltage or a current of anESD event during bonding the die to the device structure usingnon-disabled measurement devices of the plurality of measurementdevices; and probing at least one non-disabled measurement device of theplurality of measurement devices of the second set of ESD testingstructures.
 20. The method of claim 19, further comprising determining alocation of the ESD event on the die based on the captured voltage orthe captured current.